In the manufacture of semiconductor devices and other products, ion implantation systems are used to impart impurities, known as dopant elements, into semiconductor wafers, display panels, or other workpieces. Conventional ion implantation systems or ion implanters treat a workpiece with an ion beam in order to produce n- or p-type doped regions, or to form passivation layers in the workpiece. When used for doping semiconductors, the ion implantation system injects a selected ion species to produce the desired extrinsic material. For example, implanting ions generated from source materials such as antimony, arsenic, or phosphorus results in n-type extrinsic material wafers. Alternatively, implanting ions generated from materials such as boron, gallium, or indium creates p-type extrinsic material portions in a semiconductor wafer.
Conventional ion implantation systems include an ion source that ionizes a desired dopant element which is then accelerated to form an ion beam of prescribed energy. The ion beam is directed at a surface of the workpiece to implant the workpiece with the dopant element. The energetic ions of the ion beam penetrate the surface of the workpiece so that they are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity. The implantation process is typically performed in high vacuum which prevents collisions with residual gas molecules and which minimizes the risk of contamination of the workpiece by airborne particulates.
During the course of operation of the ion implantation system, a vacuum pump system operates to create a low pressure vacuum environment in one or more regions of the ion implantation system. The vacuum pump system creates a flow that inherently removes specie material and gases from the one or more regions in the ion implantation system. For purposes of the present description, the invention will be described in the context of an ion source vacuum pump system, wherein a vacuum environment is created in the region of an ion source and ion source housing. Some of the removed material often becomes deposited within the vacuum system, such as in a rough vacuum line and roughing pump of the vacuum system. Such a deposition of material can reduce the life of operation of the roughing pump. Further, in cases where source species are changed between implantations (e.g., changing from an n-type specie to a p-type specie), the change in source species can cause deleterious and/or dangerous mixing of the deposited materials in the rough and exhaust vacuum lines.
Conventionally, a mesh pad filter (e.g., stainless steel wool) is placed within the source vacuum line, wherein the mesh is intended to filter material from the vacuum system. Such mesh pads, however, are prone to accumulating material relatively quickly, thus reducing vacuum pump capabilities by restricting flow through the vacuum line, and increasing maintenance downtime incurred by filter maintenance. Further, due to the nature of the conventional mesh pads and the placement of the pad within the vacuum system, deleterious dripping or flaking of filtered material from the mesh pad into the vacuum line is common during both operation and maintenance of the filter, thus causing further problems in the roughing pump. Furthermore, when changing species of implantation, filter changes are typically necessitated in order to avoid dangerous mixing of filtered materials, thus further increasing maintenance downtime.
Accordingly, a need exists for a more robust, yet inexpensive system and methodology for removing materials in vacuum pump subsystems typically associated with ion implantation systems.